Fuzzy cognitive-based goal programming for waste rock management with in-pit dumping priority: Towards sustainable mining

Internal (in-pit) dumping is a sustainable waste rock management approach that can mitigate the potential adverse environmental, social, and economic impacts of conventional off-site dumping. In this study, a fuzzy-weighted multi-objective programming model was developed to determine the best feasible waste scheduling strategy. Minimizing waste rock hauling cost, social complaints, environmental penalties, and operational issues are the main objectives of the model. A fuzzy cognitive map was incorporated into the model to analyze the objectives based on their causal relationships. Various weighting scenarios were used to assess the influence of prioritization of objectives on the waste scheduling results. The model was applied to a surface mine containing several lens-shaped limestone deposits. It was found that entirely dumping waste rock in the internal dumps (D1-D3) could lead to the lowest social, environmental, and operational issues under the causal weights of 0.272, 0.267, 0.230, and 0.230 for the social, environmental, economic, and operational objectives, respectively. However, the distances between the extraction sites and internal dumps are large compared to external dumps (K1 and K2), and dumping in the external dumps resulted in significantly more social complaints and environmental effects. A sensitivity analysis on the capacity of the preferred internal dump (D1) indicated that if its capacity is inadequate to accommodate all wastes, the less preferable internal dumps would be used, followed by external dumps.